Lumped constant circulator

ABSTRACT

A lumped constant circulator comprising a conductor case; a central assembly consisting of a conductor assembly including at least three insulated conductor strips intersecting each other preferably at an angle of 120*, said conductor strips being each connected at one end to said conductor case and at the other end individually to a respective coaxial connector through a respective serially arranged capacitor; ferrite plates so superposed as to have said central conductor assembly sandwiched therebetween; and magnets for supplying said ferrite plates with a D.C. magnetic field acting perpendicular to their mutually facing surfaces.

United States Patent Iwase et a1.

LUMPED CONSTANT CIRCULATOR Inventors: Nobuo Iwase, Zushi; Soji Okamura,

Yokohama, both of Japan Assignee: Tokyo Shibaura Electric Co. Ltd.,

Kawasaki-shi, Japan Filed: June 1, 1972 Appl. No.: 258,801

Foreign Application Priority Data June 18, 1971 Japan 46-43316 Us. c1. 333/1.1, 333/84 M Int. Cl HOlp 1/32 Field of Search 333/1.1

References Cited UNITED STATES PATENTS 8/1967 Konishi 333/1.1 11/1971 Bosma 333/1.1

[ Jan. 29, 1974 FOREIGN PATENTS OR APPLICATIONS 18,962 8/1969 Japan 333/1.l

Primary Examiner-Paul L. Gensler Attorney, Agent, or Firm-Flynn & Frishauf [5 7] ABSTRACT A lumped constant circulator comprising a conductor case; a central assembly consisting of a conductor assembly including at least three insulated conductor strips intersecting each other preferably at an angle of 120, said conductor strips being each connected at one end to said conductor case and at the other end individually to a respective coaxial connector through a respective serially arranged capacitor; ferrite plates so superposed as to have said central conductor assembly sandwiched therebetween; and magnets for supplying said ferrite plates with a DC magnetic field acting perpendicular to their mutually facing surfaces.

7 Claims, 13 Drawing Figures LUMPED CONSTANT CIRCULATOR BACKGROUND OF THE INVENTION This invention relates to a lumped constant circulator.

As is well known, a lumped constant circulator is used as a minute power circulator for VHF and UHF bands. Such a conventional type of circulator includes, as shown in FIGS. 1A and 1B, three conductor strips intersecting each other. These conductor strips 1 are each directly connected at one end 2 to a conductor case 3 or ground conductor and at the other end 4 to said conductor case 3 through a capacitor C and also to a coaxial connector 5. Said conductor strips are sandwiched between two superposed ferrite discs 7. Above and below said superposed ferrite discs 7 are positioned magnets 8 so as to apply a D.C. magnetic field acting perpendicular to their mutually facing planes.

Where the three input terminals 9 of a circulator of the above-mentioned prior art arrangement are excited by high frequency voltages having the same phase relationship, then there is obtained, as shown in FIG. 2A an equivalent circuit of said circulator, as determined at said input terminals 9. Where the three input terminals are excited by high frequency voltages having such phase relationship that their phases shift clockwise or counterclockwise with respect to a D.C. magnetic field generated by N and S magnetic poles 8, then the ferrite discs 7 present a positive or negative magnetic permeability p. or p. to circular polarized waves. As determined at the input terminals 9, therefore, the circulator will have equivalent circuits indicated in FIGS. 28 and 2C (where L represents the inductance presented by the conductor strips when the ferrite discs 7 have a magnetic permeability of 1). Admittances y y and y corresponding to FIGS. 2A, 2B and 2C have such a relationship as illustrated on a Smith Chart of FIG. 3. Admittances y and y denote those determined at the input terminals 9 where said terminals 9 are excited by high frequency voltages having such phase relationship that their phases shift clockwise or counterclockwise under the condition in which the capacitor C is not connected between the second terminals 4 of the conductor strips 1 and the conductor case 3. Namely, when there is used a capacitor C having an adequate capacitance, the admittances y t' and y are rotated to the points and y so as to cause the admittances y y. and yto be mutually spaced 21r/3 on said Smith chart.

In the conventional circulator of the aforementioned arrangement, where an angular frequency to (central frequency) varies, the admittance y remains infinite independently of said frequency variation, whereas the admittances y and y are changed according to the magnitude of frequency variation Aw, constituting one of the reasons why said circulator is reduced in band width. The band width represents a frequency range where an input signal is attenuated dB. Accordingly, the prior art lumped constant circulator has the noticeable drawback that it has as well a specific band width as about 8 percent. The specific band width represents the ratio of the band width for the central frequency.

broaden the band width of said circulator, yet .this' method is-not deemed preferable, because it will make the circulator as a whole complicated and bulky, requiring extra cost.

SUMMARY OF THE INVENTION 7 It is accordingly the object of this invention to provide a circulator characterized by broad band width without using any external compensation circuit.

According to an aspect of this invention, there is provided a lumped constant circulator comprising a ground element; a central assembly consisting of a conductor assembly including at least three insulated conductor strips intersecting each other at a prescribed angle, said conductor strips being each connected at one end to said ground element and being each connected at the other end to a respective coaxial connector through a respective serially arranged capacitor; a ferrite member disposed at least on one side of said conductor assembly; and means for supplying said ferrite member with a D.C. magnetic field acting perpendicular to its plane.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B jointly illustrate the construction of the prior art circulator;

FIGS. 2A, 2B and 2C indicate the operation of said prior art circulator;

FIG. 3 is a Smith chart showing the admittance of said prior art circulator;

FIGS. 4A and 48 indicate the construction of a circulator according to an embodiment of the invention;

FIGS. 5A, 5B and 5C present the operation of the circulator of FIGS. 4A and 4B;

FIG. 6 is a Smith chart indicating the impedance of the circulator of FIGS. 4A and 4B; and

FIG. 7 is a curve diagram showing the frequency characteristics of said circulator of FIGS. 4A and 4B.

DETAILED DESCRIPTION OF THE INVENTION A circulator according to an embodiment of this invention shown in FIGS. 4A and 48 includes three insulated conductor strips 11 mutually intersecting at an angle of about These conductor strips are each connected at one end 12 to a conductor case or ground element 13 and at the other end 14 to a coaxial connector 15 through a serially arranged capacitor C said other end 14 being used as the input terminal 19 of the circulator. There are provided two ferrite discs 17 so superposed as to have the three conductor strips sandwiched therebetween. Above and below said ferrite discs 17 are disposed magnets 18 for externally supplying the ferrite discs 17 with a D.C. magnetic field acting perpendicular to their mutually facing planes.

Where the three input terminals 19 of the circulator of the above-mentioned arrangement are excited by high frequency voltages having the same phase relationship, then there is obtained, as shown in FIG. 5A, an equivalent circuit of said circulator, as determined at the input terminals 19. Where the three terminals 19 are excited by high frequency voltages having such phase relationship that their phases shift clockwise or counterclockwise with respect to a D.C. magnetic field generated by the magnets 18, then the ferrite discs 17 indicate a positive or negative magnetic permeability p." or p. to circular polarized waves. Accordingly, there are obtained equivalent'circuits of FIGS. 5A, 5B and 5C, as determined at the input terminals 19. Referring to FIGS. 5B and 5C, L denotes the degree of inductance presented by the conductor strips 11 when the ferrite discs 17 have a magnetic permeability of l. The impedances Z Z and Z corresponding to FIGS. A, 5B and 5C have such a relationship as shown on a Smith chart of FIG. 6. When the impedance components [.U'L and p. I and capacitance C are chosen to have a proper magnitude, then the impedances Z Z and Z- are spaced 21r/3 on the Smith chart.

Where an angular frequency (central frequency) w varies by Aw, then the impedances Z Z and Z respectively present variations AZ AZ, and AZ expressed as follows:

AZ jAwL' AZ- =jAw(L' iL) where:

The impedance variations AZ AZ and AZ caused by the frequency variation Aw are all inductive, though of different magnitude and rotate in the same direction on the Smith chart of FIG. 6, enabling the circulator of this invention fully to effect its function even with certain frequency variations and to display prominently improved frequency characteristics due to broadened band width.

FIG. 7 indicates an instance of the determined frequency characteristics of a three-port circulator according to an embodiment of this invention. The curve I shows the attenuation characteristics of an output signal from a second port derived from an input signal conducted to, for example, a first port. The curve II illustrates the isolation characteristics of a signal leaking from a third port at that time. In this case the central frequency is set at 550 MHZ. As is apparent from FIG. 7, the band width is about 70 MHZ or about 13 percent of the specific band width. This is about 1.5 times broader than is possible with the prior art circulator.

As mentioned above, this invention provides a circulator characterized by broad band width without using any external compensation circuit. The foregoing description refers to an embodiment of the invention, and should not be understood to impose any limitation thereon.

For example, the conductor strips formed of loop conductor elements may each be replaced by a single thin conductor plate or two thin superposed conductor plates connected by wires at both ends.

What we claim is:

1. A lumped constant circulator comprising:

a ground element;

a central assembly consisting of:

a conductor assembly including at least three insulated conductor strips intersecting each other at a prescribed angle; and

at least three capacitors, the total number of capacitors being exactly the same as the number of said conductor strips, each capacitor being connected only in series with a respective one of said conductor strips;

said conductor strips being jointly connected at one end to said ground element, and the other ends thereof being each individually connected to a respective coaxial connector through a serially arranged one of said capacitors;

a ferrite member disposed at least on one side of said conductor assembly; and

means for supplying the ferrite member with a DC.

magnetic field acting perpendicular to that surface of said ferrite member which faces the central conductor assembly.

2. The circulator according to claim 1 wherein the conductor assembly consists of three conductor strips intersecting each other at an angle of and said at least three capacitors consist of only three capacitors, each being connected in series with a respective one of said three conductor strips.

3. The circulator according to claim 2 wherein the three conductor strips intersect each other such that one of them passes over one of the remaining ones and under the other of said remaining ones.

4. The circulator according to claim 1 wherein each of the conductor strips comprises conductor elements disposed side by side.

5. The circulator according to claim 1 wherein the ground conductor comprises a conductor case in which there are received the central assembly and said ferrite member.

6. The circulator according to claim 1 including a ferrite member disposed on each side of said conductor assembly.

7. The circulator according to claim 6 wherein the ground conductor comprises a conductor case in which there are received the central assembly and said ferrite members.

* t III 

1. A lumped constant circulator comprising: a ground element; a central assembly consisting of: a conductor assembly including at least three insulated conductor strips intersecting each other at a prescribed angle; and at least three capacitors, the total number of capacitors being exactly the same as the number of said conductor strips, each capacitor being connected only in series with a respective one of said conductor strips; said conductor strips being jointly connected at one end to said ground element, and the other ends thereof being each individually connected to a respective coaxial connector through a serially arranged one of said capacitors; a ferrite member disposed at least on one side of said conductor assembly; and means for supplying the ferrite member with a D.C. magnetic field acting perpendicular to that surface of said ferrite member which faces the central conductor assembly.
 2. The circulator according to claim 1 wherein the conductor assembly consists of three conductor strips intersecting each other at an angle of 120* ; and said at least three capacitors consist of only three capacitors, each being connected in series with a respective one of said three conductor strips.
 3. The circulator according to claim 2 wherein the three coNductor strips intersect each other such that one of them passes over one of the remaining ones and under the other of said remaining ones.
 4. The circulator according to claim 1 wherein each of the conductor strips comprises conductor elements disposed side by side.
 5. The circulator according to claim 1 wherein the ground conductor comprises a conductor case in which there are received the central assembly and said ferrite member.
 6. The circulator according to claim 1 including a ferrite member disposed on each side of said conductor assembly.
 7. The circulator according to claim 6 wherein the ground conductor comprises a conductor case in which there are received the central assembly and said ferrite members. 